1. Field of the Invention
The present invention relates to a semiconductor device, particularly to a semiconductor device having a lead terminal on only one side of a package.
2. Description of the Related Art
As shown in FIG. 1, a conventional semiconductor device is formed by radially connecting a lead 21 protruded from a margin 29a inside of a body to the inside 29 of the body with a pad 24 on a semiconductor chip 22 by a bonding wire 23. Therefore, the pattern of the lead 21 has a regular simple shape. Thus, it is possible to easily set a suspension pin 26 for holding an island 25 to mount a semiconductor chip 22 inside of the body 29 between patterns of the lead 21 and at four sides of the island 25 as illustrated. As a result, the island 25 is stably located without tilting in a resin sealing step and therefore, it is possible to easily form a package.
However, because an electronic unit circuit has more complicated and advanced functions, to attain high speed operation and reduction of the mounting area, the lead terminal of a package and the arrangement of pads of a semiconductor chip are specialized and the pattern of a lead frame is complicated. For example, as shown in FIG. 2, there is a case in which a lead terminal 30 is provided for only one side of a package, e.g., a zigzag inline package (ZIP). In this case, because it is necessary for a power-supply terminal pad to stably supply a power supply voltage to the whole of a chip 32, a power-supply-voltage pad 34b is also present on the side opposite to the lead terminal side. To bond the opposite-side pad 34b, it is necessary to extend the lead frame from the side where the lead terminal 30 is present and arrange a lead 31a enclosing the chip 32. Therefore, it is impossible to provide a suspension pin 36 for holding an island 35 for necessary portions around the island, that is, right and left sides of an island 35 in this case.
In the case of the above-described conventional semiconductor device, when the lead terminal 30 can be provided for only one side of the package and the pad on the chip is also present on the side opposite to the lead terminal, it is necessary to arrange leads extended so as to enclose the chip by extending the lead frame from the side where the lead terminal is present. Therefore, it is impossible to provide a joint (suspension pin) for holding the island for necessary portions around the island. Thus, there is a disadvantage that the number of joints decreases, the island becomes unstable and tilts in the resin sealing step, and finally the island protrudes from the package.